1. Field of the Invention
The invention relates to a method for operating a gas pressure vessel, commonly termed an autoclave, for use in hot isostatic pressing operations.
2. Description of the Prior Art
It is well known to produce various alloy articles, such as articles of high speed steel, titanium, and super alloys, by compacting alloy powder charges in a hot isostatic pressing vessel, commonly termed an autoclave, to consolidate the articles to densities substantially 100% of theoretical density. Since autoclaves are of expensive construction and operation, it is advantageous from the standpoint of providing an economical manufacturing practice to provide for reduced time between pressing operations to in turn increase the autoclave production rate. This results in a lowering of the costs per cycle of the product produced by operation of the autoclave.
Various practices have been employed to achieve increased production rates. Specifically, practices have been employed for quickly pressurizing the autoclave, such as the use of cryogenic liquid pumps that discharge into a vaporizer to produce gas at high pressures required for the hot isostatic compaction operation. These systems convert a cryogenic liquid, such as argon which is at a relatively low pressure, into a gas at a suitably high pressure for compacting. This gas, which is discharged from a vaporizer, is introduced into the autoclave to pressurize it to the desired level for the compacting operation. In addition, practices for reducing the time for cooling the autoclave so that the consolidated product may be removed therefrom have been used to shorten the cycle time. These include flow devices, such as a fan or heat exchange, used singly or in combination, installed in the base of the autoclave for accelerating the cooling of the autoclave at the conclusion of the hot isostatic compaction operation. Although these devices are effective for the purpose, they require equipment that reduces the interior space of the vessel to in turn reduce the capacity thereof.